The fluid torque converter has good self-adaptability and continuously changing speed and torque function. It cushions and absorbs shock to the transmission system. It does not suffer from mechanical wear, is highly reliable, and has a long service life. Thus it is widely used in the mechanical field, including automobiles and engineering and building machines.
However, the fluid torque converter is affected by the conflict between its torque changing capability and transmission efficiency. In many cases, the slow-start and the output torque can not meet the requirements. The transmission efficiency of the fluid torque converter is very low under high torque and low rotational speed, when a cooling system must be equipped to keep down the heat, making the system complex in structure, big in size and heavy in weight.
There are many types of variable speed transmission that are currently used in vehicles, such as the hand-operated speed variable transmission, the steel belt continuously variable speed transmission and the hydraulic automatic speed variable transmission. Among these, the hydraulic automatic speed variable transmissions are most frequently used. The hydraulic automatic variable speed transmission includes a fluid torque converter and a planet gearbox or a parallel-axis gearbox. The fluid torque converter can change the torque ratio within a certain range automatically and continuously. However, the factor of torque variation is not large enough and its transmission efficiency is low at low speed ratio, while the conflict exists concurrently between the torque variation capacity and the transmission efficiency. Thus the fluid torque converter used to be equipped with gearbox. However, efficiency and speed are both sacrificed during the shifts of the speed changing gearbox, and several clutch, brake and control mechanism must be added to support the shifts, making the variable speed transmission heavy in weight, complex in structure and big in size, etc.
The Sine Continuously Variable Speed Transmission is a continuously variable speed transmission with totally new mechanism. It can realize zero-start, continuously speed changing and very high start torque, and also achieve a very high torque ratio when the rotational speed ratio is low. It is highly efficient, simple in structure, small in size and light in weight. The Sine Constantly Variable Speed Transmission has been published in Chinese Patent Applications, namely, No. 200410091908.4 entitled “Oscillation type of continuously variable speed transmission”, No. 200510034124.2 entitled “Rollway one direction clutch wheel and the continuously variable speed transmission of using the rollway one direction clutch wheel”, No. 200510035453.9 entitled “The variable speed transmission with balance”, No. 200510036495.4 entitled “Automatic continuously variable speed transmission”, and No. 200620013327.3 entitled “Self-adaptable continuously variable speed transmission used in manpower vehicle and the manpower vehicle with this variable speed transmission”, and some improvement schemes have been made in these patent applications. However, the Sine Constantly Variable Speed Transmission shows shortages of decreasing trend of efficiency when working at high speed ratio. Those above mentioned patent applications are hereby incorporated by reference as if set forth in their entirety.